Electrical power transfer assembly

ABSTRACT

An assembly for an aircraft including a first structure mounted to a second structure, and a power transfer assembly electrically connecting the first and second structures. The first structure is movable relative to the second structure between a retracted and an extended position. The power transfer assembly includes a housing, a spool mounted for rotation relative to the housing and biased to rotate in a first direction, and an electrical cable adapted to be wound around the spool when the spool rotates, such that movement of the first structure from its retracted to its extended position causes the cable to be unwound from the spool by rotation of the spool in a second direction opposite the first. Also, a method of electrically connecting the first and second structures. The invention may be applied to an aircraft wing to electrically connect a leading edge slat to a fixed airfoil portion.

RELATED APPLICATIONS

The present application is based on, and claims priority from, BritishApplication Number GB0913128.5, filed Jul. 29, 2009, the disclosure ofwhich is hereby incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention relates to an assembly for an aircraft comprisinga first structure mounted to a second structure, and a power transferassembly electrically connecting the first and second structures,wherein the first structure is movable relative to the second structurebetween a retracted and an extended position.

BACKGROUND OF THE INVENTION

Ice protection of aircraft leading edge structures has traditionallybeen provided on large commercial aircraft through the use of bleed air.Smaller aircraft have used combinations of inflatable rubber de-icingboots, and de-icing fluid. Helicopters have had significant experienceof electrical ice protection solutions. Most previous applications ofhelicopter electrical ice protection have been on fixed structures,which by definition do not move. The only exception to this beingelectrical ice protection on helicopter rotor blades where the power istransmitted through a slip ring system of joints, the technology ofwhich is used over much of the engineering industry.

There is now a move to incorporate electrical de-icing systems intocommercial fixed wing aircraft. The areas of commercial fixed wingaircraft that have particular need for ice protection are the movableleading edge slat structures.

Electrical power is transferred for other reasons across mechanicallyactuated joints. This is traditionally achieved in a variety of ways.For example, a folding arm type joint may have an electrical cablewithin each arm connected by a slip ring type rotary joint between thearms, which rotates as the arms are extended. A telescopic tube may havea helically wound electrical cable therein, similar to a telephonecable, the effective length of which changes with telescoping of thetube. An electrical cable may alternatively be encased by chain links,which limit the bend radius of the cable as the ends of the chain linksare moved towards and away from one another.

The current technological options suffer various disadvantages of beingheavy, having a high space requirement, causing fretting of anelectrical cable, or excessive manipulation of an electrical cable whichcan cause electrical wires of the cable to break, leading to reliabilityissues.

WO2006/027624A describes a coupling arrangement for coupling servicesbetween an aircraft wing fixed aerofoil component and a extendableleading edge slat mounted thereto. The coupling arrangement includes ahousing for connection to the fixed aerofoil structure, and a hollowtelescopic assembly extendable between a retracted and an extendedposition. A service carrying conduit arrangement carries the services,such as electrical power cables, between the fixed aerofoil componentand the leading edge slat, and extends through the hollow telescopicassembly. The service carrying conduit arrangement is flexible andexcess thereof is located within the housing when the telescopicassembly is in the retracted position. The excess weight and spacerequirements of the housing for storing the excess of the flexibleconduit, together with the manipulation of the electrical cables withinthe conduit when stored in the housing, exemplifies some of the problemswith prior art solutions.

There is therefore a need in the art for an improved system forelectrically connecting structures movable relative to one another.

SUMMARY OF THE INVENTION

A first aspect of the invention provides an assembly for an aircraftcomprising a first structure mounted to a second structure, and a powertransfer assembly electrically connecting the first and secondstructures, wherein the first structure is movable relative to thesecond structure between a retracted and an extended position, andwherein the power transfer assembly comprises a housing, a spool mountedfor rotation with respect to the housing and biased to rotate in a firstdirection, and an electrical cable adapted to be wound around the spoolwhen the spool rotates in the first direction, such that movement of thefirst structure from its retracted to its extended position causes thecable to be unwound from the spool by rotation of the spool in a seconddirection opposite the first.

A further aspect of the invention provides a method of electricallyconnecting a first structure mounted to a second structure, wherein thefirst structure is movable relative to the second structure between aretracted and an extended position, the method comprising:

-   -   physically and electrically connecting a power transfer assembly        between the first and second structures, the power transfer        assembly comprising a housing, a spool mounted for rotation with        respect to the housing and biased to rotate in a first        direction, and an electrical cable adapted to be wound around        the spool when the spool rotates in the first direction; and    -   moving the first structure from its retracted to its extended        position accompanied by corresponding unwinding of the cable        from the spool by rotation of the spool in a second direction        opposite the first.

The present invention is advantageous in that the power transferassembly is more lightweight, more compact and more reliable. The use ofa cable spool leads to significant space savings when compared withfolding arm connections, or extending/retracting chain links.Significant reliability improvement is provided by the elimination ofexcessive cable manipulation within the power transfer assembly.

The power transfer assembly may further comprise a spiral springconnected to the spool and to the housing for biasing the spool torotate in the first direction. This provides a compact biasing solutionwith good reliability. Alternatively, other biasing means such as ahelical spring may be used.

The power transfer assembly may further comprise an electricalconnection terminal having a first portion fixed to the housing and asecond portion rotatable with the spool, wherein the first and secondportions are electrically connected, and the second portion isphysically connected to one end of the cable. Electrical systems may beconnected to the cable via the electrical connection terminal, whichprovides a reliable electrical connection.

The cable is preferably wound with a single full turn around the spoolwhen the first structure is in its retracted position. The spoolpreferably has a diameter large enough to accommodate sufficientretracted cable length in a single full turn and to ensure the bendradius of the cable is sufficiently large, whilst being small enough tofit within a confined space. Where a greater length of retracted cableneeds to be stored on the spool, the cable may be wound as a helix ofmultiple adjacent turns. Alternatively, if space dimensions allow, thecable may be wound as a spiral of multiple concentric turns.

The power transfer assembly housing preferably includes a pair of sideplates one on either side of the spool. These side plates constrain thecable when wound about the spool and may be used to mount the housing toeither the first structure or the second structure.

Preferably, the cable includes a bundle of power and signal routes.These routes may be bundled in groups and may be shielded to protect thesignals in the signal routes from interference by the power routes.Alternatively, the cable could include a bundle of only power or signalroutes.

A free end of the cable preferably has an electrical connection terminalfor ease of connection or disconnection. The free end of the cable isthat at the end of the unwound portion of the cable.

In a preferred embodiment, the power transfer assembly has a modularconstruction so that it may be installed, serviced and replaced easily.In particular, the power transfer assembly can be provided as a cassetteincorporating the profile of the surrounding structure to which it ismounted.

The power transfer assembly housing may be mounted to either the firststructure or the second structure, as desired.

In a preferred embodiment, the first and second structures areelectrically connected by a plurality of the power transfer assemblies.Each power transfer assembly may be substantially identical. Theplurality of power transfer assemblies may be arranged side by side.

The assembly may further comprise an actuator connected between thefirst and second structures for moving the first structure between itsretracted and extended positions. Unwinding of the cable from the spoolmay be driven passively by movement of the first structure from itsretracted to its extended position.

In a preferred embodiment, the first structure is a flight controlsurface and the second structure is a fixed aerofoil structure of anaircraft. The fixed aerofoil structure may include a cut-out in itsaerodynamic leading edge through which the cable passes. The cut-outsneed only be slightly larger than the diameter of the cable to providesufficient clearance, and so they have minimal aerodynamic impact.Preferably, the cut-out is sealed around the cable by a sealing member.In particular, the first structure may be a leading edge slat and thesecond structure may be a fixed portion of an aircraft wing. Thisenables the slat to be disassembled easily without also having todisassemble the fixed leading edge. Also, there is no need for an opencut-out in the fixed leading edge, unlike the prior art power transfersolutions.

This invention has broad application and may be used to electricallyconnect virtually any pair of structures that are mounted together andare movable relative to one other. For example, the structures may beparts of a main oleo strut of an aircraft landing gear. In this case,the assembly may be used to supplying electrical power from the aircraftto, for example, an electrical wheel braking assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described with reference to theaccompanying drawings, in which:

FIG. 1 illustrates a partial 3-D view of an aircraft wing leading edgehaving slats movable between extended and retracted positions, andshowing typical power and signal electrical routing in the fixed wingleading edge;

FIG. 2 illustrates a partial cut-away view of the wing leading edgeshowing a power transfer assembly electrically connecting the slat tothe fixed wing leading edge, with the power transfer assembly and theslat in their retracted positions;

FIG. 3 illustrates a partial cut-away view of the wing leading edgeshowing the power transfer assembly and the slat in their extendedpositions;

FIG. 4 a illustrates a 3-D view of the power transfer assembly; and FIG.4 b illustrates an exploded 3-D view of the power transfer assembly;

FIG. 5 illustrates how a cable of the power transfer assembly isconnected to the electrical routing of the fixed wing structure;

FIG. 6 illustrates a 3-D view of a seal member used to seal between thecable and a cut-out in the fixed wing leading edge through which thecable passes;

FIG. 7 illustrates cut-outs in the fixed leading edge D-nose panel andin the slat trailing edge panel for receiving the cables of two powertransfer assemblies;

FIG. 8 illustrates a partial cut-away 3-D view of the wing leading edgelooking forward from below and showing the two power transfer assemblieselectrically connecting the extended slat to the fixed wing structure;and FIG. 8 a shows Detail A of FIG. 8;

FIG. 9 illustrates a schematic view of the electrical connections of thepower transfer assembly;

FIG. 10 illustrates generically a connection between one wire of thecable and the connection terminal of the power transfer assembly; andFIGS. 10 a and 10 b illustrate first and second variants respectively ofthe connection; and

FIG. 11 illustrates an alternative embodiment in which the powertransfer assembly housing is mounted to the fixed wing structure.

DETAILED DESCRIPTION OF EMBODIMENT(S)

FIG. 1 shows an aircraft wing leading edge. The aircraft wing includes afixed aerofoil structure 1 having a leading edge “D-nose” panel 2. In acavity 3 behind the D-nose panel 2 runs a power route 4 and a signalroute 5 for electrically controlling aircraft systems on the wing.

The aircraft wing further includes a plurality of leading edge slats 6mounted to the fixed aerofoil structure 1. The slats 6 aretranslationally movable relative to the fixed aerofoil structure 1between a retracted position (shown in full line) and an extendedposition (shown in broken line). The slat 6 is driven between itsretracted and extended positions by a conventional actuator (not shown).The slats 6 have an array of electro-thermal heater mats 7 for providingde-icing protection to the slat leading edge. The electro-thermal heatermats 7 are electrically controlled via the power route 4 and the signalroute 5 using one or more power transfer assemblies 8.

FIG. 2 shows one of the power transfer assemblies located in a cavitybehind the leading edge of the slat 6. The power transfer assembly 8includes a cable 9 having an electrical connector terminal 10 which isthreadably connected to a mating electrical connector terminal 11 of thefixed aerofoil structure 1. FIG. 2 shows the slat 6 in its retractedposition and FIG. 3 shows the slat 6 in its extended, or deployed,position in which a slot 12 is opened up between the slat 6 and thefixed aerofoil structure 1. When the slat 6 is in its retracted positionas shown in FIG. 2, the cable 9 is wound about a spool 13 of the powertransfer assembly 8. As the slat 6 is moved from its retracted positionto its extended position as shown in FIG. 3, the cable 9 is unwound fromthe spool 13 such that an unwound portion of the cable 9 bridges theslot 12 between the slat 6 and the fixed aerofoil structure 1. In thisway, it is possible to provide electrical control to the electro-thermalheater mats 7 even when the slat 6 is in its extended position.

The power transfer assembly 8 will now be described in greater detailwith respect to FIGS. 4 a and 4 b. The power transfer assembly 8comprises a housing 14 a, 14 b, a spool 13 mounted for rotation withrespect to the housing 14 a, 14 b and biased to rotate in a firstdirection by a pair of steel spiral springs 15 a, 15 b. The electricalcable 9 is adapted to be wound around the spool 13 when the spoolrotates in the first direction. The spiral springs 15 a, 15 b areretained in grooves 16 at either end of the spool 13 (Only one groove isvisible in FIG. 4 b).

The power transfer assembly 8 further includes an electrical connectionterminal comprising a first stator portion 17 fixed to the housing 14 a,14 b, and a second rotor portion 18 rotatable with the spool 13. Therotor and stator portions 17, 18 are electrically connected byrespective connection pads 17 a, 18 a, which will be described ingreater detail below. The stator portion 17 is connected to theelectro-thermal heater mats 7 and the rotor portion 18 is connected toone end of the cable 9.

The cable 9 is wound with a single full turn around the spool 13 whenthe power transfer assembly is in its retracted position. The cable 9includes a bundle of power and signal routes. There may be several tensor even in excess of a hundred individual power and/or signal routeswithin the cable bundle. Due to the large number of individual wiringroutes within the cable 9, the diameter of the spool 13 is relativelylarge so as to prevent excessive manipulation of the cable which couldcause fatigue damage and result in failure of at least one of the wiringroutes within the cable bundle. A minimum bend radius criteria istherefore applied for the cable 9 on the spool 13 such that the bendradius is six times the diameter of the cable. The cable typically has adiameter of around ten millimetres but may be greater or smaller thanthis depending on the number of individual wiring routes required.

FIG. 5 shows one of the power transfer assemblies 8 installed in theslat 6 ready for connection to the fixed aerofoil structure 1. Two suchpower transfer assemblies 8 are used to connected the slat 6 to thefixed aerofoil structure 1. The construction of the power transferassembly 1 facilitates a modular slat design philosophy whereby as manyslat components as possible are preinstalled in the slat 6 prior tomounting to the fixed aerofoil structure 1 during final assembly of anew aircraft. This design philosophy also has benefits in terms ofimproved serviceability during the aircraft's operational lifetime.

As shown in FIG. 5, the unconnected cable 9 is initially biased by thespiral springs 15 a, 15 b to be wound around the spool 13. The modularslat 6 is mounted to the fixed aerofoil structure 1 by means of aconventional slat actuation mechanism (not shown). The slat actuationmechanism typically includes a slat track on which the slat 6 movesrelative to the fixed aerofoil structure 1 under control of an actuator.Once the slat 6 has been mounted to the fixed aerofoil structure 1, thefree end of the cable 9 of the power transfer assembly 8 having theelectrical connector terminal 10 is pulled against the biasing action ofthe spiral springs 15 a, 15 b to unwind at least a portion of the cable9 from the spool 13. With the cable 9 at least partially unwound, theelectrical connector terminal 10 is connected to the electricalconnector terminal 11. The electrical connector terminals 10, 11 areco-operating standard threaded terminals. The electrical connectorterminal 11 is fixed to one end of a cable 20 which is electricallyconnected to the power and/or signal routes 4, 5 in the leading edge ofthe fixed aerofoil structure 1.

The electrical connector terminal 11 is located just behind theaerodynamic leading edge of the fixed aerofoil structure 1. So that theconnector terminal 10 may be threadably connected to the terminal 11, acut-out 21 is formed in the aerodynamic leading edge of the fixedaerofoil structure 1. The free end of the cable 9 having the connectorterminal 10 is sealed within the cut-out 21 by a seal member 22, shownin FIG. 6. The seal member 22 prevents fretting of the cable 9, providesa flat landing surface for the terminal 11, and provides a goodaerodynamic and weatherproof seal in the leading edge of the fixedaerofoil structure 1. The seal member 22 has a sealing flange 23 aroundan aperture 24. The cable 9 is passed through the aperture 24 and thesealing flange 23 sits against the rear surface of the D-nose panel 2around the periphery of the cut-out 21. The seal member 22 is made ofinjection moulded thermoplastic material.

Since the power transfer assembly 8 is mounted within the slat 6, thecable 9 must also pass through a rear panel 25 of the slat 6. The slatrear panel 25 therefore also has a cut-out 26 which receives the cable9. FIG. 7 shows a schematic view of the D-nose panel 2 of the fixedaerofoil structure 1 and the rear panel 25 of the slat 6. Two cut-outs21 are provided in the D-nose panel 2 and two cut-outs 26 are providedin the slat rear panel 25. Each pair of cut-outs 21, 26 is adapted toreceive a respective cable 9 of each of the power transfer assemblies 8.

FIG. 8 shows a cut away view of the fixed aerofoil structure 1 with theslat 6 in its extended position electrically connected by the two powertransfer assemblies 8. FIG. 8 a shows Detail A of FIG. 8. In FIGS. 8 and8 a, the seal members 22 in the cut-outs 21 are not shown. The housing14 a, 14 b of each power transfer assembly 8 can be seen through thecut-outs 26 in the slat rear panel 25. Where two power transferassemblies are provided, as shown, one of these may carry a bundle ofpower routes and the other may carry a bundle of signal routes forconnection to the power and signal routes 4, 5, respectively. However,it will be appreciated by those skilled in the art that more than twopower transfer assemblies may be provided to connect the slat 6 to thefixed aerofoil structure 1; each power transfer assembly 8 may carryboth power and signal routes; or only a single power transfer assembly 8may be provided to electrically connect the slat 6 and the fixedaerofoil structure 1, depending on requirements.

It is to be noted that the cut-outs 21 in the D-nose panel 2 aresignificantly smaller than would be required for a prior art folding armtype power transfer assembly, which significantly reduces aerodynamicdrag, noise and fuel consumption of the aircraft. The cut-outs 21, 26are ovoid to account for the vertical change in orientation of the cable9 within these cut-outs during deployment of the slat 6 from itsretracted to its extended position. The cut-outs 26 in the rear slatpanel 25 may also have a rubber seal (not shown) around the periphery ofthe cut-out to prevent fretting of the cable 9.

FIG. 9 shows a schematic cross section view through the power transferassembly 8 showing the electrical connection on one side of a centrelineC. The cable 9 is wound between the side plates 14 a, 14 b of thehousing and carries a bundle of wiring routes electrically connected tothe power or signal routes 4, 5 of the fixed aerofoil structure 1. Atthe end of the cable 9 fixed to the spool 13, individual wiring routesof the cable bundle are electrically connected to the rotor portion 18of the electrical connection terminal by connections 27. Theseconnections will be described in greater detail with reference to FIGS.10, 10 a and 10 b below.

Connection pads 18 a of the rotor portion 18 interface with theconnection pads 17 a of the stator portion 17 of the electricalconnection terminal. The stator portion 17 is bonded to the side plates14 a, 14 b. The rotor portion 18 is rotatable with respect to the sideplates 14 a, 14 b within limits defined by the steel spiral springs 15a, 15 b connected between the rotor portion 18 and the side walls 14 a,14 b which sit in the grooves 16 in the rotor portion 18. A threadedelectrical connection socket 28 is fixed to the stator portion 17 and iselectrically connected to the stator portion 17 by connections 29. Theseconnections 29 are similar to the connections 27.

The threaded electrical connection socket 28 is threadably connected toa mating threaded electrical connection socket 36 fixed to one end of aslat cable 30 which is electrically connected to electrical equipment,such as the electro-thermal heating mats 7 and lighting, for example, ofthe slat 6.

FIG. 10 shows schematically one of the connections 27 between anindividual wiring route and the electrical connection terminal 17, 18.FIGS. 10 a and 10 b show two alternative variants of the connection 27which may be used. In the variant shown in FIG. 10 a the rotor portion18 has a local connector portion 31 having a hole 32 which receives anexposed electrically conductive end of an individual wiring route of thecable bundle 9 and which is held in place in the hole 32 by tightening ascrew 33. In the variant shown in FIG. 10 b, the screw 33 is omitted andthe exposed electrically conductive end of the individual wiring routelocated within the hole 32 is welded in place to form the electricalconnection with the rotor portion 18.

In the embodiment described above, the power transfer assembly orassemblies 8 are mounted within the slat cavity. However, in accordancewith a second embodiment of this invention as depicted in FIG. 11, thepower transfer assembly or assemblies are installed in the leading edgeof the fixed aerofoil structure. As shown in FIG. 11, a slat 106 ismounted to the leading edge of a fixed aerofoil portion 101 and is shownin its extended position forward of the D-nose panel 102. The fixedaerofoil structure 101 includes a “D-rib” 134 of a conventional type andeach power transfer assembly 108 is attached or bonded to one of theseD-ribs 134 located span-wise across the wing leading edge.

The second embodiment differs from the first embodiment essentially onlyin that the power transfer assembly is attached to the fixed aerofoilstructure rather than to the slat. In addition, to prevent fretting ofthe cable 109, a roller element 135 is located just behind the D-nosepanel 102 over which the cable 109 passes as the slat 106 is movedbetween its extended and retracted positions. The configuration of thesecond embodiment shown in FIG. 11 may be used where there isinsufficient space within the slat cavity to accommodate the powertransfer assembly, or where it is desirable to do so for other reasons.

Due to the large aerodynamic forces experienced in the region betweenthe slat and the fixed aerofoil structure when the slat is in itsextended position, it may be necessary to constrain the cable of thepower transfer assembly to prevent or reduce impact and excessivevibration of the unwound portion of the cable. The unwound portion ofthe cable may be housed within a telescoping tube arrangement, or theunwound portion of the cable may be slidably connected to the slatactuation mechanism. For example, where the slat actuation mechanismincludes a slat track, the slat track may be fitted with one or moreswivel clips which retain the unwound portion of the cable which isfreely slidable within the clips. The exact construction of these andalternative retaining means will be readily appreciated by those skilledin the art.

Whilst the spool of the power transfer assembly preferably has adiameter large enough to accommodate sufficient retracted cable lengthin a single full turn, where a greater length of retracted cable lengthneeds to be stored on the spool, the cable may be wound as a helix ofmultiple adjacent turns on the spool. Alternatively, the cable may bewound as a spiral of concentric turns upon the spool.

Whilst in the embodiments described above the power transfer assembly isused to electrically connect a slat to a fixed aerofoil portion of anaircraft wing, this invention has broad application and may be used toelectrically connect virtually any pair of structures that are mountedtogether and are movable relative to one another. For example, thestructures may be parts of a main oleo strut of an aircraft landinggear. In this case, the assembly may be used to supply electrical powerfrom the aircraft to, for example, an electrical wheel breakingassembly.

Although the invention has been described above with reference to one ormore preferred embodiments, it will be appreciated that various changesor modifications may be made without departing from the scope of theinvention as defined in the appended claims.

1. An assembly for an aircraft, comprising: a flight control surface mounted to a fixed aerofoil structure, a power transfer assembly electrically connecting the flight control surface and the fixed aerofoil structure, wherein the flight control surface is movable translationally relative to the fixed aerofoil structure between a retracted and an extended position, wherein the power transfer assembly comprises a housing, entirety a spool mounted for rotation with respect to the housing and biased to rotate in a first direction, and an electrical cable adapted to be wound around the spool when the spool rotates in the first direction, such that movement of the flight control surface from its retracted to its extended position causes the cable to be unwound from the spool by rotation of the spool in a second direction opposite the first direction, and, wherein the fixed aerofoil structure includes a cut-out in its aerodynamic leading edge through which the cable passes and the cut-out is sealed around the cable by a seal, wherein said seal permits said cable to deflect at said seal upon the deployment of the flight control surface.
 2. An assembly according to claim 1, wherein the power transfer assembly further comprises a spiral spring connected to the spool and to the housing for biasing the spool to rotate in the first direction.
 3. An assembly according to claim 1, wherein the power transfer assembly further comprises an electrical connection terminal having a first portion fixed to the housing and a second portion rotatable with the spool, wherein the first and second portions are electrically connected, and the second portion is physically connected to one end of the cable.
 4. An assembly according to claim 1, wherein the cable is wound with a single full turn around the spool when the first structure is in its retracted position.
 5. An assembly according to claim 1, wherein the housing includes a pair of side plates one on either side of the spool.
 6. An assembly according to claim 1, wherein the cable includes a bundle of power and signal routes.
 7. An assembly according to claim 1, wherein a free end of the cable has an electrical connection terminal.
 8. An assembly according to claim 1, wherein the power transfer assembly has a modular construction.
 9. An assembly according to claim 1, wherein the power transfer assembly housing is mounted to either the flight control surface or the fixed aerofoil structure.
 10. An assembly according to claim 1, wherein the flight control surface and the fixed aerofoil structure are electrically connected by a plurality of the power transfer assemblies.
 11. An assembly according to claim 1, further comprising an actuator connected between the flight control surface and the fixed aerofoil structure for moving the flight control surface between its retracted and extended positions.
 12. An assembly according to claim 1, wherein unwinding of the cable from the spool is driven passively by movement of the flight control surface from its retracted to its extended position.
 13. A method of electrically connecting a flight control surface mounted to a fixed aerofoil structure, wherein the flight control surface is movable translationally relative to the fixed aerofoil structure between a retracted and an extended position, the method comprising: physically and electrically connecting a power transfer assembly between the flight control surface and the fixed aerofoil structure, the power transfer assembly comprising a housing, a spool mounted for rotation with respect to the housing and biased to rotate in a first direction, and an electrical cable adapted to be wound around the spool when the spool rotates in the first direction; providing a cut-out in an aerodynamic leading edge of the fixed aerofoil structure through which the cable passes; sealing the cut-out around the cable with a seal, wherein said seal permits said cable to deflect at said seal upon the deployment of the flight control surface, and moving the flight control surface from its retracted to its extended position accompanied by corresponding unwinding of the cable from the spool by rotation of the spool in a second direction opposite the first. 